The overall objective of our research in this area is the investigation of the metabolic fates of cannabis constituents in vivo in the rabbit, the monkey and ultimately in humans. This will involve completion of our present study with delta- tetrahydrocannabinol in the animals. A series of experiments with differently labelled THC derivatives will then be done to check for hitherto undetected metabolites. Finally, a study will be done on human subjects using the animal data as a guide. The specific goal of the research is to establish the chemical structures of the urinary metabolite(s). This information is of vital importance for the development of sensitive specific assay procedures for use in clinical and forensic medicine. It is also important in the investigation of structure-activity relationships and the general pharmacology of marihuana.